1. Field of the Invention
This invention relates to electronic control units, and more specifically, to electronic control units that are located in, or in the vicinity of, a high temperature heat source such as an internal combustion engine.
2. Description of the Related Art
Generally, electronic control units, such as those working as control devices for use with internal combustion engines on vehicles, have circuit boards on which are mounted heat dissipating devices such as semiconductor switching devices. These circuit boards are housed in a chassis made of metallic materials such as aluminum alloys. Such electronic control units maintain the heat dissipating devices at temperatures below a predetermined temperature by conducting heat generated during circuit board operation from the inside of the circuit board to the outside of the chassis.
In prior art configurations, because the surface of the metal components forming the chassis is a natural metallic surface, the amount of heat transfer to the chassis from the heat dissipating devices mounted on the circuit board is small.
In recent years, there has been a need to develop a technique for decreasing the size of the engine compartment, for resource savings and other purposes, and installing engine components in the compartment in a concentrated fashion. Whether or not they are mounted on a high temperature heat source such as an internal combustion engine, electronic control units are expected to be compact and dissipate heat efficiently. However, the component structure can become complex and sufficient installation space must be ensured if the heat transfer from heat dissipating devices to the chassis is to be realized by heat conduction via the circuit board, for example. It then becomes difficult to reduce the size of the electronic control unit.